ENB PDCCH implementation to avoid ambiguous DCI information

ABSTRACT

A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus determines a first starting index for transmitting first control information in a first search space, determines a second starting index for transmitting second control information in a second search space, and transmits the second control information in the second search space at the second starting index when the first starting index and the second starting index are not the same value. The apparatus further transmits to a user equipment (UE) control information in a first search space, receives information from the UE corresponding to the transmitted control information, and decodes the received information based on the UE parsing the control information according to the first search space and based on the UE incorrectly parsing the control information according to a second search space.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. patent application Ser. No.14/023,438, entitled “ENB PDCCH IMPLEMENTATION TO AVOID AMBIGUOUS DCIINFORMATION” and filed on Sep. 10, 2013, which claims the benefit ofU.S. Provisional Application Ser. No. 61/748,731, entitled “ENB PDCCHIMPLEMENTATION TO AVOID AMBIGUOUS DCI INFORMATION” and filed on Jan. 3,2013, and U.S. Provisional Application Ser. No. 61/753,900, entitled“ENB PDCCH IMPLEMENTATION TO AVOID AMBIGUOUS DCI INFORMATION” and filedon Jan. 17, 2013. U.S. patent application Ser. No. 14/023,438, the U.S.Provisional Application Ser. No. 61/748,731, and the U.S. ProvisionalApplication Ser. No. 61/753,900 are expressly incorporated by referenceherein in their entireties.

BACKGROUND Field

The present disclosure relates generally to communication systems, andmore particularly, to mitigating ambiguity of downlink controlinformation when a physical downlink control channel (PDCCH) candidateis transmitted in a user equipment specific search space (UESS) orcommon search space (CSS).

Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency division multiple access (SC-FDMA) systems, andtime division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is Long Term Evolution (LTE). LTE is a set ofenhancements to the Universal Mobile Telecommunications System (UMTS)mobile standard promulgated by Third Generation Partnership Project(3GPP). LTE is designed to better support mobile broadband Internetaccess by improving spectral efficiency, lowering costs, improvingservices, making use of new spectrum, and better integrating with otheropen standards using OFDMA on the downlink (DL), SC-FDMA on the uplink(UL), and multiple-input multiple-output (MIMO) antenna technology.However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

In an aspect of the disclosure, a method, a computer program product,and an apparatus are provided. The apparatus determines a first startingindex for transmitting first control information in a first searchspace, determines a second starting index for transmitting secondcontrol information in a second search space, and transmits the secondcontrol information in the second search space at the second startingindex when the first starting index and the second starting index arenot the same value.

In a further aspect, the apparatus transmits to a UE control informationin a first search space, receives information from the UE correspondingto the transmitted control information, and decodes the receivedinformation based on the UE parsing the control information according tothe first search space and based on the UE incorrectly parsing thecontrol information according to a second search space.

In another aspect, the apparatus determines a first aggregation levelhaving a number of control channel elements (CCEs) used for firstcontrol information in a first search space, transmits second controlinformation in a second search space using a second aggregation levelhaving a lower value than the first aggregation level, wherein thesecond search space is enclosed within the first search space, andwherein a starting CCE for the first control information in the firstsearch space is the same as a starting CCE for the second controlinformation in the second search space, determines at least one CCE ofthe first aggregation level not used for transmitting the second controlinformation, and transmits interference on the at least one unused CCEto degrade decoding of the first control information in the first searchspace.

In yet another aspect, the apparatus determines a first starting indexfor transmitting a first control message in a first search space,determines a second starting index for transmitting a second controlmessage in a second search space, and when the first starting index andthe second starting index have the same value, determines at least oneinformation field different between the first control message and thesecond control message, and sets a bit of the at least one differentinformation field to zero in the first control message and the secondcontrol message.

In an aspect, the apparatus generates first control information fortransmitting in a first search space, codes the first controlinformation, wherein the code applied to the first control informationis specific to the first search space and different from code applied tosecond control information in a second search space, and transmits thecoded first control information in the first search space.

In another aspect, the apparatus generates control information in afirst search space, determines a size of a first payload including thegenerated control information for the first search space, adjusts thesize of the first payload to be different from a second payload for asecond search space, and transmits the first payload having the adjustedsize in the first search space.

In a further aspect, the apparatus generates first control informationfor transmitting in a first search space. For a first subset ofsubframes, the apparatus assigns a first priority to the first controlinformation in the first search space, the first priority higher than asecond priority assigned to second control information in a secondsearch space, and transmits the first control information with theassigned first priority in the first search space. For a second subsetof subframes, the apparatus assigns a third priority to the firstcontrol information in the first search space, the third priority lowerthan a fourth priority assigned to the second control information in thesecond search space, and transmits the first control information withthe assigned third priority in the first search space.

In yet a further aspect, the apparatus determines a first decodingcandidate (e.g., first PDCCH candidate) in a first search space and asecond decoding candidate (e.g., second PDCCH candidate) in a secondsearch space, where the first decoding candidate and the second decodingcandidate have a same size but different definitions of informationfields, identifies a difference in the information fields, anddetermines one of the first decoding candidate and the second decodingcandidate as a valid candidate based on the identified difference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture.

FIG. 2 is a diagram illustrating an example of an access network.

FIG. 3 is a diagram illustrating an example of a DL frame structure inLTE.

FIG. 4 is a diagram illustrating an example of an UL frame structure inLTE.

FIG. 5 is a diagram illustrating an example of a radio protocolarchitecture for the user and control planes.

FIG. 6 is a diagram illustrating an example of an evolved Node B anduser equipment in an access network.

FIG. 7A discloses a continuous carrier aggregation type.

FIG. 7B discloses a non-continuous carrier aggregation type.

FIG. 8 is a flow chart of a method of wireless communication.

FIG. 9 is a flow chart of a method of wireless communication.

FIG. 10 is a flow chart of a method of wireless communication.

FIG. 11 is a flow chart of a method of wireless communication.

FIG. 12 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 13 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 14 is a flow chart of a method of wireless communication.

FIG. 15 is a flow chart of a method of wireless communication.

FIG. 16 is a flow chart of a method of wireless communication.

FIG. 17 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 18 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 19 is a flow chart of a method of wireless communication.

FIG. 20 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 21 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, modules, components,circuits, steps, processes, algorithms, etc. (collectively referred toas “elements”). These elements may be implemented using electronichardware, computer software, or any combination thereof. Whether suchelements are implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented with a “processing system”that includes one or more processors. Examples of processors includemicroprocessors, microcontrollers, digital signal processors (DSPs),field programmable gate arrays (FPGAs), programmable logic devices(PLDs), state machines, gated logic, discrete hardware circuits, andother suitable hardware configured to perform the various functionalitydescribed throughout this disclosure. One or more processors in theprocessing system may execute software. Software shall be construedbroadly to mean instructions, instruction sets, code, code segments,program code, programs, subprograms, software modules, applications,software applications, software packages, routines, subroutines,objects, executables, threads of execution, procedures, functions, etc.,whether referred to as software, firmware, middleware, microcode,hardware description language, or otherwise.

Accordingly, in one or more exemplary embodiments, the functionsdescribed may be implemented in hardware, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on or encoded as one or more instructions or code on acomputer-readable medium. Computer-readable media includes computerstorage media. Storage media may be any available media that can beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer. Disk and disc, as used herein, includescompact disc (CD), laser disc, optical disc, digital versatile disc(DVD), and floppy disk where disks usually reproduce data magnetically,while discs reproduce data optically with lasers. Combinations of theabove should also be included within the scope of computer-readablemedia.

FIG. 1 is a diagram illustrating an LTE network architecture 100. TheLTE network architecture 100 may be referred to as an Evolved PacketSystem (EPS) 100. The EPS 100 may include one or more user equipment(UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS)120, and an Operator's Internet Protocol (IP) Services 122. The EPS caninterconnect with other access networks, but for simplicity thoseentities/interfaces are not shown. As shown, the EPS providespacket-switched services, however, as those skilled in the art willreadily appreciate, the various concepts presented throughout thisdisclosure may be extended to networks providing circuit-switchedservices.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108.The eNB 106 provides user and control planes protocol terminationstoward the UE 102. The eNB 106 may be connected to the other eNBs 108via a backhaul (e.g., an X2 interface). The eNB 106 may also be referredto as a base station, a Node B, an access point, a base transceiverstation, a radio base station, a radio transceiver, a transceiverfunction, a basic service set (BSS), an extended service set (ESS), orsome other suitable terminology. The eNB 106 provides an access point tothe EPC 110 for a UE 102. Examples of UEs 102 include a cellular phone,a smart phone, a session initiation protocol (SIP) phone, a laptop, apersonal digital assistant (PDA), a satellite radio, a globalpositioning system, a multimedia device, a video device, a digital audioplayer (e.g., MP3 player), a camera, a game console, a tablet, or anyother similar functioning device. The UE 102 may also be referred to bythose skilled in the art as a mobile station, a subscriber station, amobile unit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology.

The eNB 106 is connected to the EPC 110. The EPC 110 includes a MobilityManagement Entity (MME) 112, other MMES 114, a Serving Gateway 116, aMultimedia Broadcast Multicast Service (MBMS) Gateway 124, a BroadcastMulticast Service Center (BM-SC) 126, and a Packet Data Network (PDN)Gateway 118. The MME 112 is the control node that processes thesignaling between the UE 102 and the EPC 110. Generally, the MME 112provides bearer and connection management. All user IP packets aretransferred through the Serving Gateway 116, which itself is connectedto the PDN Gateway 118. The PDN Gateway 118 provides UE IP addressallocation as well as other functions. The PDN Gateway 118 is connectedto the Operator's IP Services 122. The Operator's IP Services 122 mayinclude the Internet, an intranet, an IP Multimedia Subsystem (IMS), anda PS Streaming Service (PSS). The BM-SC 126 is the source of MBMStraffic. The MBMS Gateway 124 distributes the MBMS traffic to the eNBs106, 108.

FIG. 2 is a diagram illustrating an example of an access network 200 inan LTE network architecture. In this example, the access network 200 isdivided into a number of cellular regions (cells) 202. One or more lowerpower class eNBs 208 may have cellular regions 210 that overlap with oneor more of the cells 202. The lower power class eNB 208 may be a femtocell (e.g., home eNB (HeNB)), pico cell, micro cell, or remote radiohead (RRH). The macro eNBs 204 are each assigned to a respective cell202 and are configured to provide an access point to the EPC 110 for allthe UEs 206 in the cells 202. There is no centralized controller in thisexample of an access network 200, but a centralized controller may beused in alternative configurations. The eNBs 204 are responsible for allradio related functions including radio bearer control, admissioncontrol, mobility control, scheduling, security, and connectivity to theserving gateway 116.

The modulation and multiple access scheme employed by the access network200 may vary depending on the particular telecommunications standardbeing deployed. In LTE applications, OFDM is used on the DL and SC-FDMAis used on the UL to support both frequency division duplexing (FDD) andtime division duplexing (TDD). As those skilled in the art will readilyappreciate from the detailed description to follow, the various conceptspresented herein are well suited for LTE applications. However, theseconcepts may be readily extended to other telecommunication standardsemploying other modulation and multiple access techniques. By way ofexample, these concepts may be extended to Evolution-Data Optimized(EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interfacestandards promulgated by the 3rd Generation Partnership Project 2(3GPP2) as part of the CDMA2000 family of standards and employs CDMA toprovide broadband Internet access to mobile stations. These concepts mayalso be extended to Universal Terrestrial Radio Access (UTRA) employingWideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA;Global System for Mobile Communications (GSM) employing TDMA; andEvolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSMare described in documents from the 3GPP organization. CDMA2000 and UMBare described in documents from the 3GPP2 organization. The actualwireless communication standard and the multiple access technologyemployed will depend on the specific application and the overall designconstraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. Theuse of MIMO technology enables the eNBs 204 to exploit the spatialdomain to support spatial multiplexing, beamforming, and transmitdiversity. Spatial multiplexing may be used to transmit differentstreams of data simultaneously on the same frequency. The data steamsmay be transmitted to a single UE 206 to increase the data rate or tomultiple UEs 206 to increase the overall system capacity. This isachieved by spatially precoding each data stream (i.e., applying ascaling of an amplitude and a phase) and then transmitting eachspatially precoded stream through multiple transmit antennas on the DL.The spatially precoded data streams arrive at the UE(s) 206 withdifferent spatial signatures, which enables each of the UE(s) 206 torecover the one or more data streams destined for that UE 206. On theUL, each UE 206 transmits a spatially precoded data stream, whichenables the eNB 204 to identify the source of each spatially precodeddata stream.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas. To achieve good coverage at the edges of the cell, asingle stream beamforming transmission may be used in combination withtransmit diversity.

In the detailed description that follows, various aspects of an accessnetwork will be described with reference to a MIMO system supportingOFDM on the DL. OFDM is a spread-spectrum technique that modulates dataover a number of subcarriers within an OFDM symbol. The subcarriers arespaced apart at precise frequencies. The spacing provides“orthogonality” that enables a receiver to recover the data from thesubcarriers. In the time domain, a guard interval (e.g., cyclic prefix)may be added to each OFDM symbol to combat inter-OFDM-symbolinterference. The UL may use SC-FDMA in the form of a DFT-spread OFDMsignal to compensate for high peak-to-average power ratio (PAPR).

FIG. 3 is a diagram 300 illustrating an example of a DL frame structurein LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames.Each sub-frame may include two consecutive time slots. A resource gridmay be used to represent two time slots, each time slot including aresource block. The resource grid is divided into multiple resourceelements. In LTE, a resource block contains 12 consecutive subcarriersin the frequency domain and, for a normal cyclic prefix in each OFDMsymbol, 7 consecutive OFDM symbols in the time domain, or 84 resourceelements. For an extended cyclic prefix, a resource block contains 6consecutive OFDM symbols in the time domain and has 72 resourceelements. Some of the resource elements, indicated as R 302, 304,include DL reference signals (DL-RS). The DL-RS include Cell-specific RS(CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS)304. UE-RS 304 are transmitted only on the resource blocks upon whichthe corresponding physical DL shared channel (PDSCH) is mapped. Thenumber of bits carried by each resource element depends on themodulation scheme. Thus, the more resource blocks that a UE receives andthe higher the modulation scheme, the higher the data rate for the UE.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structurein LTE. The available resource blocks for the UL may be partitioned intoa data section and a control section. The control section may be formedat the two edges of the system bandwidth and may have a configurablesize. The resource blocks in the control section may be assigned to UEsfor transmission of control information. The data section may includeall resource blocks not included in the control section. The UL framestructure results in the data section including contiguous subcarriers,which may allow a single UE to be assigned all of the contiguoussubcarriers in the data section.

A UE may be assigned resource blocks 410 a, 410 b in the control sectionto transmit control information to an eNB. The UE may also be assignedresource blocks 420 a, 420 b in the data section to transmit data to theeNB. The UE may transmit control information in a physical UL controlchannel (PUCCH) on the assigned resource blocks in the control section.The UE may transmit only data or both data and control information in aphysical UL shared channel (PUSCH) on the assigned resource blocks inthe data section. A UL transmission may span both slots of a subframeand may hop across frequency.

A set of resource blocks may be used to perform initial system accessand achieve UL synchronization in a physical random access channel(PRACH) 430. The PRACH 430 carries a random sequence and cannot carryany UL data/signaling. Each random access preamble occupies a bandwidthcorresponding to six consecutive resource blocks. The starting frequencyis specified by the network. That is, the transmission of the randomaccess preamble is restricted to certain time and frequency resources.There is no frequency hopping for the PRACH. The PRACH attempt iscarried in a single subframe (1 ms) or in a sequence of few contiguoussubframes and a UE can make only a single PRACH attempt per frame (10ms).

FIG. 5 is a diagram 500 illustrating an example of a radio protocolarchitecture for the user and control planes in LTE. The radio protocolarchitecture for the UE and the eNB is shown with three layers: Layer 1,Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer andimplements various physical layer signal processing functions. The L1layer will be referred to herein as the physical layer 506. Layer 2 (L2layer) 508 is above the physical layer 506 and is responsible for thelink between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control(MAC) sublayer 510, a radio link control (RLC) sublayer 512, and apacket data convergence protocol (PDCP) 514 sublayer, which areterminated at the eNB on the network side. Although not shown, the UEmay have several upper layers above the L2 layer 508 including a networklayer (e.g., IP layer) that is terminated at the PDN gateway 118 on thenetwork side, and an application layer that is terminated at the otherend of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 514 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between eNBs. The RLC sublayer 512 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ). The MACsublayer 510 provides multiplexing between logical and transportchannels. The MAC sublayer 510 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNBis substantially the same for the physical layer 506 and the L2 layer508 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 516 in Layer 3 (L3 layer). The RRC sublayer 516is responsible for obtaining radio resources (i.e., radio bearers) andfor configuring the lower layers using RRC signaling between the eNB andthe UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650in an access network. In the DL, upper layer packets from the corenetwork are provided to a controller/processor 675. Thecontroller/processor 675 implements the functionality of the L2 layer.In the DL, the controller/processor 675 provides header compression,ciphering, packet segmentation and reordering, multiplexing betweenlogical and transport channels, and radio resource allocations to the UE650 based on various priority metrics. The controller/processor 675 isalso responsible for HARQ operations, retransmission of lost packets,and signaling to the UE 650.

The transmit (TX) processor 616 implements various signal processingfunctions for the L1 layer (i.e., physical layer). The signal processingfunctions include coding and interleaving to facilitate forward errorcorrection (FEC) at the UE 650 and mapping to signal constellationsbased on various modulation schemes (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded andmodulated symbols are then split into parallel streams. Each stream isthen mapped to an OFDM subcarrier, multiplexed with a reference signal(e.g., pilot) in the time and/or frequency domain, and then combinedtogether using an Inverse Fast Fourier Transform (IFFT) to produce aphysical channel carrying a time domain OFDM symbol stream. The OFDMstream is spatially precoded to produce multiple spatial streams.Channel estimates from a channel estimator 674 may be used to determinethe coding and modulation scheme, as well as for spatial processing. Thechannel estimate may be derived from a reference signal and/or channelcondition feedback transmitted by the UE 650. Each spatial stream isthen provided to a different antenna 620 via a separate transmitter618TX. Each transmitter 618TX modulates an RF carrier with a respectivespatial stream for transmission.

At the UE 650, each receiver 654RX receives a signal through itsrespective antenna 652. Each receiver 654RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 656. The RX processor 656 implements various signalprocessing functions of the L1 layer. The RX processor 656 performsspatial processing on the information to recover any spatial streamsdestined for the UE 650. If multiple spatial streams are destined forthe UE 650, they may be combined by the RX processor 656 into a singleOFDM symbol stream. The RX processor 656 then converts the OFDM symbolstream from the time-domain to the frequency domain using a Fast FourierTransform (FFT). The frequency domain signal comprises a separate OFDMsymbol stream for each subcarrier of the OFDM signal. The symbols oneach subcarrier, and the reference signal, are recovered and demodulatedby determining the most likely signal constellation points transmittedby the eNB 610. These soft decisions may be based on channel estimatescomputed by the channel estimator 658. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 610 on the physical channel. Thedata and control signals are then provided to the controller/processor659.

The controller/processor 659 implements the L2 layer. Thecontroller/processor can be associated with a memory 660 that storesprogram codes and data. The memory 660 may be referred to as acomputer-readable medium. In the UL, the controller/processor 659provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 662, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 662 for L3 processing. Thecontroller/processor 659 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets tothe controller/processor 659. The data source 667 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by the eNB 610, thecontroller/processor 659 implements the L2 layer for the user plane andthe control plane by providing header compression, ciphering, packetsegmentation and reordering, and multiplexing between logical andtransport channels based on radio resource allocations by the eNB 610.The controller/processor 659 is also responsible for HARQ operations,retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a referencesignal or feedback transmitted by the eNB 610 may be used by the TXprocessor 668 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 668 are provided to different antenna 652 via separatetransmitters 654TX. Each transmitter 654TX modulates an RF carrier witha respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar tothat described in connection with the receiver function at the UE 650.Each receiver 618RX receives a signal through its respective antenna620. Each receiver 618RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 670. The RXprocessor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. Thecontroller/processor 675 can be associated with a memory 676 that storesprogram codes and data. The memory 676 may be referred to as acomputer-readable medium. In the UL, the control/processor 675 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the UE 650. Upper layer packets fromthe controller/processor 675 may be provided to the core network. Thecontroller/processor 675 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

LTE-Advanced UEs use spectrum up to 20 MHz bandwidths allocated in acarrier aggregation of up to a total of 100 MHz (5 component carriers)used for transmission in each direction. Generally, less traffic istransmitted on the uplink than the downlink, so the uplink spectrumallocation may be smaller than the downlink allocation. For example, if20 MHz is assigned to the uplink, the downlink may be assigned 100 MHz.These asymmetric FDD assignments conserve spectrum and are a good fitfor the typically asymmetric bandwidth utilization by broadbandsubscribers.

For LTE-Advanced mobile systems, two types of carrier aggregation (CA)methods may be provided, continuous CA and non-continuous CA. They areillustrated in FIGS. 7A and 7B. Non-continuous CA occurs when multipleavailable component carriers are separated along the frequency band(FIG. 7B). On the other hand, continuous CA occurs when multipleavailable component carriers are adjacent to each other (FIG. 7A). Bothnon-continuous and continuous CA aggregate multiple LTE/componentcarriers to serve a single unit of LTE Advanced UE.

Multiple RF receiving units and multiple FFTs may be deployed withnon-continuous CA in LTE-Advanced UE since the carriers are separatedalong the frequency band. Because non-continuous CA supports datatransmissions over multiple separated carriers across a large frequencyrange, propagation path loss, Doppler shift, and other radio channelcharacteristics may vary a lot at different frequency bands.

Thus, to support broadband data transmission under the non-continuous CAapproach, methods may be used to adaptively adjust coding, modulationand transmission power for different component carriers. For example, inan LTE-Advanced system where the enhanced NodeB (eNodeB) has fixedtransmitting power on each component carrier, the effective coverage orsupportable modulation and coding of each component carrier may bedifferent.

Interpretation of a physical downlink control channel (PDCCH) downlinkcontrol information format 0 (DCI0) payload may depend on whether a UEfinds DCI0 in a common search space (CSS) or a UE specific search space(UESS). When the CSS overlaps with the UESS and a starting controlchannel element (CCE) (i.e., starting index) of the CSS is aligned witha starting CCE of the UESS, the UE may select a PDCCH candidate from theCSS when in fact the PDCCH candidate from the UESS is the intendedcandidate. This may result in the UE incorrectly parsing the DCI payloadleading to misalignment between an eNB and the UE (e.g., a mismatchbetween an actual UE behavior and a UE behavior expected by the eNB).Hence, a change in PDCCH scheduling may be needed to avoid the mismatchbetween the actual UE behavior and the UE behavior expected by the eNB.Accordingly, the present disclosure provides approaches for mitigatingthe DCI0 ambiguity.

The determination of the starting index for a control channel decodingcandidate may be based on a type of a search space, an aggregation levelassociated with the decoding candidate, a UE-specific radio networktemporary identifier (RNTI), and/or a number of control channel elements(CCEs) in a subframe. A UE may first determine a number of CCEs in asubframe. If the search space is a CSS, a set of aggregation levels anda set of decoding candidates for a given aggregation level may bedetermined. Each aggregation level consists of a number of CCEs. Forexample, a UE may determine that there are aggregation levels 4 and 8 inthe CSS, and there are four and two decoding candidates for aggregationlevels 4 and 8, respectively. The starting index for aggregation level 4for the four decoding candidates may start from 0 and be multiples offour, i.e., CCE0, CCE4, CCE8 and CCE12 for the four decoding candidatesof aggregation level 4. The starting index for aggregation level 8 forthe two decoding candidates may start from 0 and be multiples of eight,i.e., CCE0 and CCE8 for the two decoding candidates of aggregation level8. If the search space is a UESS, the UE may first determine a startingindex for an aggregation level. The starting index can be derived basedon a UE-specific RNTI, some random seeds, and the number of CCEs in thesubframe. The starting index can be different for different subframes.The starting index for an aggregation level L may be multiples of L. Asan example, in a subframe of 40 CCEs, the UE may determine that thestarting index for aggregation level 1 is 7, 8, 9, 10, 11, and 12,respectively, for six decoding candidates of aggregation level 1. The UEmay determine that the starting index for aggregation level 2 is 16, 18,20, 22, 24, and 26, respectively, for six decoding candidates ofaggregation level 2. The UE may determine that the starting index foraggregation level 4 is 28, 32, 36, and 0, respectively, for fourdecoding candidates of aggregation level 4. The UE may determine thatthe starting index for aggregation level 8 is 8 and 16, respectively,for two decoding candidates of aggregation level 8.

Wireless standard specifications (e.g., LTE standards) may provide aselection rule in case of ambiguity in determining whether a PDCCHcandidate is transmitted in the UESS or CSS. For example, the CSS may beprioritized over the UESS. Specifically, a UE configured to monitorPDCCH candidates with CRC scrambled by cell radio network temporaryidentifier (C-RNTI) or semi-persistent scheduling (SPS) C-RNTI with acommon payload size and with the same first CCE index but with differentsets of DCI information fields in the CSS and UESS on the primary cellmay assume that only the PDCCH in the CSS is transmitted by the primarycell.

The selection rule provided by the wireless standard specificationsdefines UE behavior in case of common payload and starting CCE, and maybe applied irrespective of aggregation level (AL). Specifically, the UEmay prioritize the CSS over the UESS in the case of a common payload,the same starting CCE, and either the same aggregation level ordifferent aggregation levels.

In case of the same aggregation level, same payload, and fullycoincident PDCCH resources in CSS and UESS (e.g., same start CCE), theUE may not be able to distinguish between DCI0 sent on the UESS and DCI0sent on the CSS. For example, the UE selecting the DCI0 candidate fromthe CSS may lead to misalignment between the UE and eNB when theintended DCI0 candidate is from the UESS.

In the case of different aggregation levels, with common payload, andsame start CCE, a DCI0 candidate from the CSS with a higher aggregationlevel may be seen by the UE as a DCI0 candidate in the UESS with a loweraggregation level. For example, DCI0 sent in the CSS with aggregationlevel 4 may be difficult to distinguish from DCI0 sent in the UESS withaggregation level 2 when there is a high signal-to-noise ratio (SNR) andthe starting CCE indices are the same.

PDCCH candidates comprise a number of consecutive CCEs. A PDCCH istransmitted on one or an aggregation of several consecutive CCEs.Aggregation level (AL) 1 comprises a single CCE. ALs 2, 4, and 8correspond to 2, 4, and 8 consecutive CCEs, respectively. The size of asearch space may be determined by the number of PDCCH candidates and thesize of the CCE aggregation level. For example, the size of the searchspace may be defined as the number of CCEs per PDCCH candidate times thenumber of PDCCH candidates. Hence, the search space size is a functionof aggregation level. The number of CCE aggregation levels supported bythe CSS may be limited to 4 and 8. The UESS may support CCE aggregationlevels 1, 2, 4 and 8. In general, if a lower aggregation level candidateis fully enclosed in a higher aggregation level candidate and startingCCEs and payloads are the same, similarity of post de-rate matchingmetrics across different aggregation level hypotheses may lead to the UEdecoding both candidates. In this case, reliable detection of the CSSversus the UESS can be difficult and may require a decoding decisionbased on raw data. However, a decoding decision based on raw data maysignificantly add to UE processing requirements.

In an example, when the UE is configured with two downlink frequencydivision duplex (FDD) cells, each cell having 10 MHz bandwidth, and eachcell not signaling sounding reference signals (SRS) and carrier indexfields, the payload of DCI0 for both the CSS and the UESS is 43 bits.For the CSS, a 1-bit CQI request may be used along with a padding bit.For the UESS, a 2-bit CQI request may be used with no padding. If theeNB transmits DCI0 on the UESS with aggregation level 2 and starting CCE0 so that the UESS is embedded in the CSS, the UE may not be able todistinguish between a CSS with aggregation level 4 and a UESS withaggregation level 2, and may select the CSS candidate when the UESScandidate should be selected. If, in addition, the CSI request field is“10” and the Secondary cell (Scell) belongs to trigger group 0, the UEand eNB may disagree on the number of expected CQI reports, triggering aPUSCH block error rate (BLER).

In the example above, only the CSI request field being set to “10”results in ambiguity. DCI0 with the CSI request field set to “11” or“01” will be decoded as the UESS candidates. A CSI request field set to“00” has the same interpretation for both the UESS and the CSS. To avoidambiguous behavior, regardless of aggregation level, eNB PDCCHscheduling should account for and mitigate ambiguous DCI0 decodes, aswill be discussed in the present disclosure.

In an aspect, eNB scheduling may be improved to mitigate ambiguous DCI0decodes. Since the ambiguity stems from the CSS and the UESS having asame starting CCE, regardless of aggregation level, ambiguity can beavoided by the eNB ensuring that the starting CCE for DCI0 message inthe UESS is not a starting CCE in the CSS.

For example, where a total number of available CCEs (N_(CCE)) isN_(CCE)=8, the starting CCE index for candidate m and aggregation levelL may be given by:L{(Y _(k) +m)mod └N _(CCE)┘},where Y_(k) is used to randomize the starting index as a function ofRNTI and slot number, where Y_(k) can take unique values between 0 and65536, and m is the candidate index that can take values between 0 and└N_(CCE)/L┘−1.

As mentioned in the example above, a UE may not be able to distinguish aDCI format 0 sent in the UESS using L=2 with starting index 0 from a DCIformat 0 sent in the CSS using L=4 with starting index 0.

However, the eNB may avoid such an ambiguity by: 1) Detecting theexistence of the ambiguity; and 2) Finding a starting index that avoidsthe ambiguity. It can be shown through exhaustive calculation of theabove equation that for any given distinct value of Y_(k), it ispossible to find two candidate indices m that result in a starting indexnot equal to 0 or 4 when L=2, which avoids collision with any message inthe CSS that may use L=4 or L=8.

Similarly, it can be shown that for any given distinct value of Y_(k),it is possible to find at least four candidate indices m that result ina starting index not equal to 0 or 4 when L=1, which avoids collisionwith any message in the CSS that may use L=4 or L=8. Therefore, it ispossible to implement a mechanism at the eNB scheduler where a suitablePDCCH candidate index (i.e., starting CCE) can be calculated that avoidsthis type of collision.

Alternatively, an eNB implementation may simply detect this type ofcollision and simply choose not to transmit the PDCCH that contains aDCI format 0 message that may result in ambiguous behavior in a subframebut let Y_(k) randomize the starting index at a later time to send theDCI format 0 message.

In another aspect, ambiguous DCI0 decodes may be mitigated by performingblind decoding of PUSCH across all relevant payloads corresponding tovarious numbers of CQI reports whenever there is potential forambiguity. For example, when the UE incorrectly parses (interprets afterdecoding) a DCI0 message, a corresponding PUSCH payload may not bealigned with a payload expected by the eNB. This may result inmisalignment triggering PUSCH BLER, as described above. However, if theeNB blindly decodes PUSCH across all possible payloads or a subsetaccording to the ambiguous DCI0 decodes, then the eNB will be able todecode PUSCH regardless of whether the UE parsed (interpreted) the DCI0message correctly. Hence, blind decoding allows the eNB to correctlydecode PUSCH across all possible UE interpretations of DCI0 payload.This alleviates misalignment between the eNB and the UE. Furthermore,the eNB can make a decision to retransmit the message that wasincorrectly parsed by the UE.

In a further aspect, ambiguous DCI0 decodes may be mitigated bytransmitting interference on unused CCEs of a higher aggregation level.For example, when a lower aggregation level candidate is fully enclosedin a higher aggregation level candidate with the same starting CCE andpayload, the unused CCEs in the higher aggregation level may not betransmitted, resulting in similar decoding metrics (metrics used todetermine successful decoding) between hypotheses in both search spaces.Accordingly, interference may be transmitted on the unused CCEs of thehigher aggregation level candidate to degrade the decoding metrics ofthe hypothesis for the higher aggregation level. For example,transmitting strong enough interference on the unused portion ofaggregation level 4 in the CSS results in degraded hypothesis of the CSScandidate at the UE and likely leads to the UE selecting the candidatein the UESS.

In yet another aspect, ambiguous DCI0 decodes may be mitigated byrestricting transmission fields that cause ambiguity. The eNB may unifyDCI0 message parsing across UE and common search spaces when there isambiguity. For instance, in the example described above, the eNB mayrefrain from setting a CSI request field to “10” to avoid the ambiguity.

For example, the following rule can be used at the eNB: If the decodingcandidate in the UESS has a same starting CCE as the CSS, set all fieldsthat potentially cause ambiguity to values resulting in commoninterpretation between DCIs associated with the CSS and the DCIsassociated with the UESS. For instance, for information fields in DCIformat 0 that include an aperiodic CSI triggering field, an aperiodicSRS triggering field, and a multi-cluster assignment flag field, the eNBmay set the corresponding fields (or bits) to zero, such thatA-CSI/A-SRS/Multi-cluster are not enabled.

In an aspect, any information fields that are present only in the UESSmay be placed towards the end of the corresponding DCI (e.g., located ata latter part of a series of fields of the corresponding DCI). This maymaximize the commonality of information between DCI in the CSS and DCIin the UESS such that restriction on the transmission of informationfields to avoid ambiguity is minimized.

In an aspect, wireless standard specification approaches address DCI0payloads that potentially cause ambiguity. A payload potentially causesambiguity when the payload 1) is valid for both CSS and UESS; and 2)yields different UE behavior depending on whether the payload isdetected in CSS or UESS.

To avoid the payload ambiguity, the UESS and CSS may explicitly bedistinguished by modifying a coding implementation between the UESS andCSS. This may be accomplished by: 1) implementing different ratematching for UESS than CSS; 2) implementing different interleaving forUESS than CSS; or 3) scrambling UESS cyclic redundancy check (CRC). Theabove solutions may be backward-compatible with LTE Release 10 UEs orfuture LTE releases by providing UE capability field(s) advertisingsupport. If supported by the UE, the network may use differentiatedcoding or scrambling across CSS and UESS by signaling to the UEactivation of the differentiated scrambling or coding.

The UE may signal its capability for differentiated coding or scramblingas follows. The UE can advertise support for differentiated coding(e.g., CRC scrambling, rate matching, etc.) in UESS by using aUECapabilityInformation RRC message. This message containsUE-EUTRA-Capability used to convey UE capability parameters. A field canbe added to signal UE capability for PDCCH decoding in UESS. The addedfield may indicate which PDCCH coding of UESS is supported by the UE.The decision to use differentiated coding in UESS is up to the eNB. TheeNB may use a RadioResourceConfigDedicated RRC message to enabledifferentiated coding. For example, a field may be added to aPhysicalConfigDedicated information element to convey that CRCscrambling is enabled.

Alternatively, to avoid the payload ambiguity, a UESS payload may bedistinguished from a CSS payload. This may be accomplished by ensuringthat the respective payload sizes are different. For example, wheneverthe UESS and CSS contents may result in payload ambiguity, padding bitsmay be added to ensure that the payload sizes are also different. Thissolution may be backward-compatible with existing UEs by providing UEcapability field(s) advertising support.

In a further alternative, CSS and UESS may be prioritized dependent on asubframe. For example, in case of ambiguity, CSS may be prioritized overUESS in subframes where UE system information (e.g., paging and SIB) islikely to be received by the UE. Meanwhile, UESS may be prioritized overCSS in other subframes.

For example, in a first set of subframes (e.g., subframes 0, 4, 5, and 9for a frequency division duplex (FDD) system and subframes 0, 1, 5, and6 for a time division duplex (TDD) system), CSS has a priority higherthan a priority of UESS. In the remaining set of subframes, UESS has apriority higher than a priority of CSS. This allows CSS to provide afallback operation when the eNB is reconfiguring the UE, and the UE doesnot have knowledge of new features being activated.

In an aspect, prioritization may be performed such that under someconditions, CSS is assigned a higher priority, while under otherconditions, UESS is assigned a higher priority. For example,prioritization between a first DCI from a CSS and a second DCI from aUESS, when the first and the second DCIs have a same size and samestarting CCE but different information contents, may be dependent on thedifference in the information contents.

For example, the second DCI may contain a cross-carrier scheduling (CIF)information field. This information field may be present at thebeginning of the DCI. Accordingly, the first DCI may be assigned ahigher priority, such that a fallback operation based on the first DCIis possible.

In another example, the second DCI may contain a 2-bit channel stateinformation (CSI) request field compared with a 1-bit CSI request fieldin the first DCI. This information field may be present towards the endof the DCI (e.g., located at a latter part of a series of fields of theDCI). Accordingly, the second DCI may be assigned a higher priority toallow a more likely usage of the 2-bit CSI request, without asignificant impact on the fallback operation. For instance, the fallbackoperation may still be performed by transmitting the control channelusing a minimum common set of information fields between the first DCIand the second DCI, while setting some or all of the bits correspondingto the distinct information fields between the first DCI and the secondDCI such that there is effectively no ambiguity in the informationconveyed by the control channel.

FIG. 8 is a flow chart 800 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 802,the base station determines a first starting index (e.g., first startingCCE) for transmitting first control information (e.g., first PDCCH DCI0message) in a first search space. At step 804, the base stationdetermines a second starting index (e.g., second starting CCE) fortransmitting second control information (e.g., second PDCCH DCI0message) in a second search space. In an aspect, the first search spaceis a common search space (CSS) and the second search space is a userequipment specific search space (UESS). Alternatively, the first searchspace may be the UESS and the second search space may be the CSS.

The first starting index may be determined based on at least a candidateindex and an aggregation level corresponding to the first search spaceused for transmitting the first control information. The second startingindex may be determined based on at least a candidate index and anaggregation level corresponding to the second search space fortransmitting the second control information. Accordingly, the basestation may select the at least one candidate index for determining thesecond starting index such that a value of the second starting index isnot the same as a value of the first starting index.

For example, where a starting CCE index for candidate m and aggregationlevel L is given by:L{(Y _(k) +m)mod └N _(CCE)┘},where Y_(k) is used to randomize the starting index as a function ofRNTI and slot number, where Y_(k) can take unique values between 0 and65536, and m is the candidate index that can take values between 0 and└N_(CCE)/L▪−1, the base station may select a value of m for determiningthe second starting CCE index such that a value of the second startingCCE index is not the same as a value of the first starting CCE index.

At step 806, the base station determines whether the value of the firststarting index is the same as the value of the second starting index.The determination may be performed by comparing the first starting indexvalue to the second starting index value. At step 808, when the firststarting index and the second starting index are not the same value, thebase station transmits the second control information in the secondsearch space at the second starting index.

When the first starting index and the second starting index are the samevalue, at step 810, the base station refrains from transmitting thesecond control information in the second search space at the secondstarting index. Thereafter, at step 812, the base station determines athird starting index for transmitting the second control information inthe second search space. The base station may determine the thirdstarting index not using a starting index value that is the same as thefirst starting index value. Finally, at step 814, the base stationtransmits the second control information in the second search space atthe third starting index when the first starting index and the thirdstarting index are not the same value.

FIG. 9 is a flow chart 900 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 902,the base station transmits to a user equipment (UE) control informationin a first search space. The control information may be transmitted inthe first search space at a starting index that is the same as astarting index for transmitting second control information in a secondsearch space. The first search space may be a user equipment specificsearch space (UESS) and the second search space may be a common searchspace (CSS). Alternatively, the first search space may be the CSS andthe second search space may be the UESS.

At step 904, the base station receives information from the UEcorresponding to the transmitted control information. At step 906, thebase station decodes the received information based on the UE parsingthe control information according to the first search space. The basestation also decodes the received information based on the UEincorrectly parsing the control information according to the secondsearch space. Finally, at step 908, the base station may retransmit thecontrol information to the UE in the first search space when the basestation learns that the UE incorrectly parsed the control informationaccording to the second search space.

FIG. 10 is a flow chart 1000 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 1002,the base station determines a first aggregation level having a number ofcontrol channel elements (CCEs) used for first control information in afirst search space.

At step 1004, the base station transmits second control information in asecond search space using a second aggregation level having a lowervalue than the first aggregation level. The second search space may beenclosed within the first search space. Moreover, a starting CCE fortransmitting the first control information in the first search space isthe same as a starting CCE for transmitting the second controlinformation in the second search space. The first search space may be auser equipment specific search space (UESS) and the second search spacemay be a common search space (CSS). Alternatively, the first searchspace may be the CSS and the second search space may be the UESS.

At step 1006, the base station determines at least one CCE of the firstaggregation level not used for transmitting the control information. Atstep 1008, the base station transmits interference on the at least oneunused CCE to degrade decoding of the first control information in thefirst search space.

FIG. 11 is a flow chart 1100 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 1102,the base station determines a first starting index (e.g., a firststarting CCE) for transmitting a first control message (e.g., firstPDCCH message) in a first search space. At step 1104, the base stationdetermines a second starting index (e.g., a second starting CCE) fortransmitting a second control message (e.g., second PDCCH message) in asecond search space. In an aspect, the first search space is a commonsearch space (CSS) and the second search space is a user equipmentspecific search space (UESS). Alternatively, the first search space maybe the UESS and the second search space may be the CSS.

At step 1106, the base station determines whether a value of the firststarting index is the same as a value of the second starting index. Whenthe first starting index and the second starting index are not the samevalue, the base station transmits the second control information in thesecond search space at the second starting index (step 1112).

When the first starting index and the second starting index have thesame value, at step 1108, the base station determines at least oneinformation field different between the first control message and thesecond control message. At step 1110, the base station sets a bit of theat least one different information field to zero in the first controlmessage and the second control message. Thereafter, at step 1112, thebase station transmits the second control message in the second searchspace at the second starting index.

FIG. 12 is a conceptual data flow diagram 1200 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 1202. The apparatus may be a base station (e.g., an eNB). Theapparatus includes a receiving module 1204, a control informationgenerating module 1206, a starting index determining module 1208, aninformation processing module 1210, an aggregation level determiningmodule 1212, an interference generating module 1214, and a transmissionmodule 1216.

The starting index determining module 1208 determines a first startingindex (e.g., first starting CCE) for first control information (e.g.,first PDCCH DCI0 message) in a first search space. The starting indexdetermining module 1208 also determines a second starting index (e.g.,second starting CCE) for second control information (e.g., second PDCCHDCI0 message) in a second search space. In an aspect, the first searchspace is a common search space (CSS) and the second search space is auser equipment specific search space (UESS). Alternatively, the firstsearch space may be the UESS and the second search space may be the CSS.

The first starting index may be determined based on at least a candidateindex and an aggregation level corresponding to the first search spaceused for the first control information. The second starting index may bedetermined based on at least a candidate index and an aggregation levelcorresponding to the second search space for the second controlinformation. Accordingly, the starting index determining module 1208 mayselect the at least one candidate index for determining the secondstarting index such that a value of the second starting index is not thesame as a value of the first starting index.

The starting index determining module 1208 further determines whetherthe value of the first starting index is the same as the value of thesecond starting index. When the first starting index and the secondstarting index are not the same value, the control informationgenerating module 1206 transmits (via transmission module 1216) thesecond control information in the second search space at the secondstarting index.

When the first starting index and the second starting index are the samevalue, the control information generating module 1206 refrains fromtransmitting the second control information in the second search spaceat the second starting index. Thereafter, the starting index determiningmodule 1208 determines a third starting index for transmitting thesecond control information in the second search space. The startingindex determining module 1208 may determine the third starting index byavoiding to use a starting index that has the same value as the firststarting index. Finally, the control information generating module 1206transmits the second control information in the second search space atthe third starting index when the first starting index and the thirdstarting index are not the same value.

In an aspect, the control information generating module 1206 transmits(via transmission module 1216) to a UE 1250 control information in afirst search space. The control information may be transmitted in thefirst search space at a starting index that is the same as a startingindex for second control information in a second search space. The firstsearch space may be a user equipment specific search space (UESS) andthe second search space may be a common search space (CSS).Alternatively, the first search space may be the CSS and the secondsearch space may be the UESS.

The information processing module 1210 receives (via receiving module1204) information from the UE 1250 corresponding to the transmittedcontrol information. The information processing module 1210 decodes thereceived information based on the UE 1250 parsing the controlinformation according to the first search space. The informationprocessing module 1210 also decodes the received information based onthe UE 1250 incorrectly parsing the control information according to thesecond search space. Finally, the control information generating module1206 may retransmit (via transmission module 1216) the controlinformation to the UE 1250 in the first search space when the apparatus1202 learns that the UE 1250 incorrectly parsed the control informationaccording to the second search space.

In a further aspect, the aggregation level determining module 1212determines a first aggregation level having a number of control channelelements (CCEs) used for first control information in a first searchspace. Thereafter, the control information generating module 1206transmits second control information in a second search space using asecond aggregation level having a lower value than the first aggregationlevel. The second search space may be enclosed within the first searchspace. Moreover, a starting CCE for the first control information in thefirst search space is the same as a starting CCE for the second controlinformation in the second search space. The first search space may be auser equipment specific search space (UESS) and the second search spacemay be a common search space (CSS). Alternatively, the first searchspace may be the CSS and the second search space may be the UESS.

The interference generating module 1214 determines at least one CCE ofthe first aggregation level not used for the second control information.Accordingly, the interference generating module 1214 transmitsinterference on the at least one unused CCE to degrade decoding of thefirst control information in the first search space.

In another aspect, the starting index determining module 1208 determinesa first starting index (e.g., first starting CCE) for a first controlmessage (e.g., first PDCCH message) in a first search space. Thestarting index determining module 1208 also determines a second startingindex (e.g., second starting CCE) for a second control message (e.g.,second PDCCH message) in a second search space. In an aspect, the firstsearch space is a common search space (CSS) and the second search spaceis a user equipment specific search space (UESS). Alternatively, thefirst search space may be the UESS and the second search space may bethe CSS.

The starting index determining module 1208 further determines whether avalue of the first starting index is the same as a value of the secondstarting index. When the first starting index and the second startingindex are not the same value, the control information generating module1206 transmits (via transmission module 1216) the second controlinformation in the second search space at the second starting index.

When the first starting index and the second starting index have thesame value, the control information generating module 1206 determines atleast one information field different between the first control messageand the second control message. Thereafter, the control informationgenerating module 1206 sets a bit of the at least one differentinformation field to zero in the first control message and the secondcontrol message. Finally, the control information generating module 1206transmits the second control message in the second search space at thesecond starting index.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow charts of FIGS. 8-11.As such, each step in the aforementioned flow charts of FIGS. 8-11 maybe performed by a module and the apparatus may include one or more ofthose modules. The modules may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 13 is a diagram 1300 illustrating an example of a hardwareimplementation for an apparatus 1202′ employing a processing system1314. The processing system 1314 may be implemented with a busarchitecture, represented generally by the bus 1324. The bus 1324 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1314 and the overalldesign constraints. The bus 1324 links together various circuitsincluding one or more processors and/or hardware modules, represented bythe processor 1304, the modules 1204, 1206, 1208, 1210, 1212, 1214,1216, and the computer-readable medium 1306. The bus 1324 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 1314 may be coupled to a transceiver 1310. Thetransceiver 1310 is coupled to one or more antennas 1320. Thetransceiver 1310 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1310 receives asignal from the one or more antennas 1320, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1314, specifically the receiving module 1204. Inaddition, the transceiver 1310 receives information from the processingsystem 1314, specifically the transmission module 1216, and based on thereceived information, generates a signal to be applied to the one ormore antennas 1320. The processing system 1314 includes a processor 1304coupled to a computer-readable medium 1306. The processor 1304 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium 1306. The software, when executedby the processor 1304, causes the processing system 1314 to perform thevarious functions described supra for any particular apparatus. Thecomputer-readable medium 1306 may also be used for storing data that ismanipulated by the processor 1304 when executing software. Theprocessing system further includes at least one of the modules 1204,1206, 1208, 1210, 1212, 1214, and 1216. The modules may be softwaremodules running in the processor 1304, resident/stored in the computerreadable medium 1306, one or more hardware modules coupled to theprocessor 1304, or some combination thereof. The processing system 1314may be a component of the eNB 610 and may include the memory 676 and/orat least one of the TX processor 616, the RX processor 670, and thecontroller/processor 675.

In one configuration, the apparatus 1202/1202′ for wirelesscommunication includes means for determining a first starting index forfirst control information in a first search space, means for determininga second starting index for second control information in a secondsearch space, means for transmitting the second control information inthe second search space at the second starting index when the firststarting index and the second starting index are not the same value,means for selecting at least one candidate index for determining thesecond starting index that results in a value of the second startingindex that is not the same as a value of the first starting index, meansfor refraining from transmitting the second control information in thesecond search space at the second starting index when the first startingindex and the second starting index are the same value, means fordetermining a third starting index for the second control information inthe second search space by avoiding to use a starting index that has thesame value as the first starting index, means for transmitting thesecond control information in the second search space at the thirdstarting index when the first starting index and the third startingindex are not the same value, means for transmitting to a user equipment(UE) control information in a first search space, means for receivinginformation from the UE corresponding to the transmitted controlinformation, means for decoding the received information based on the UEparsing the control information according to the first search space andbased on the UE incorrectly parsing the control information according toa second search space, means for retransmitting the control informationto the UE in the first search space, means for determining a firstaggregation level having a number of control channel elements (CCEs)used for first control information in a first search space, means fortransmitting second control information in a second search space using asecond aggregation level having a lower value than the first aggregationlevel, wherein the second search space is enclosed within the firstsearch space, and wherein a starting CCE for the first controlinformation in the first search space is the same as a starting CCE forthe second control information in the second search space, means fordetermining at least one CCE of the first aggregation level not used forthe control information, means for transmitting interference on the atleast one unused CCE to degrade decoding of the first controlinformation in the first search space, means for determining a firststarting index for a first control message in a first search space,means for determining a second starting index for a second controlmessage in a second search space, when the first starting index and thesecond starting index have the same value, means for determining atleast one information field different between the first control messageand the second control message, means for setting a bit of the at leastone different information field to zero in the first control message andthe second control message, and means for transmitting the secondcontrol message in the second search space at the second starting index.

The aforementioned means may be one or more of the aforementionedmodules of the apparatus 1202 and/or the processing system 1314 of theapparatus 1202′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1314 mayinclude the TX Processor 616, the RX Processor 670, and thecontroller/processor 675. As such, in one configuration, theaforementioned means may be the TX Processor 616, the RX Processor 670,and the controller/processor 675 configured to perform the functionsrecited by the aforementioned means.

FIG. 14 is a flow chart 1400 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 1402,the base station generates first control information for transmitting ina first search space. At step 1404, the base station codes the firstcontrol information, wherein the coding applied to the first controlinformation is specific to the first search space and different fromcoding applied to second control information in a second search space.The first search space may be a user equipment specific search space(UESS) and the second search space may be a common search space (CSS).

The coding may be applied to the first control information when thefirst control information and the second control information have a sameset of information fields. Alternatively, the coding may be applied tothe first control information when the first control information and thesecond control information have different sets of information fields.

Applying the coding to the first control information may include atleast one of: 1) applying rate matching to the first controlinformation, wherein the rate matching applied to the first controlinformation is specific to the first search space and different fromrate matching applied to the second control information in the secondsearch space; 2) interleaving the first control information, wherein theinterleaving applied to the first control information is specific to thefirst search space and different from interleaving applied to the secondcontrol information in the second search space; or 3) scrambling thefirst control information, wherein the scrambling applied to the firstcontrol information is specific to the first search space and differentfrom scrambling applied to the second control information in the secondsearch space. Scrambling the first control information may includescrambling a cyclic redundancy check (CRC) of a first message carryingthe first control information, wherein the scrambling applied to the CRCof the first message is specific to the first search space and differentfrom scrambling applied to the CRC of a second message in the secondsearch space. For example, scrambling may be performed by applying abit-wise exclusive-or (XOR) operation on CRC bits using a scramblingsequence. A scrambling sequence may be specific to the first searchspace and different from a scrambling sequence specific to the secondsearch space. The scrambling sequence may be a pseudo-random sequence.For example, the scrambling sequence may be generated using a Goldsequence generator, where a Gold sequence generator initialization forthe first search space is different from a Gold sequence generatorinitialization for the second search space.

At step 1406, the base station informs a user equipment (UE) of thecoding applied to the first control information specific to the firstsearch space. At step 1408, the base station transmits the coded firstcontrol information in the first search space.

FIG. 15 is a flow chart 1500 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 1502,the base station generates control information for transmitting in afirst search space. At step 1504, the base station determines a size ofa first payload including the generated control information for thefirst search space.

At step 1506, the base station adjusts the size of the first payload tobe different from a second payload for a second search space. The firstsearch space may be a user equipment specific search space (UESS) andthe second search space may be a common search space (CSS). Theadjusting the size of the first payload may include adding padding bitsto the first payload to ensure that the size of the first payload isdifferent from the size of the second payload. Also, the size of thefirst payload may be adjusted when the first payload and the secondpayload have a same set of information fields. Alternatively, the sizeof the first payload is adjusted when the first payload and the secondpayload have different sets of information fields.

At step 1508, the base station transmits the first payload having theadjusted size in the first search space.

FIG. 16 is a flow chart 1600 of a method of wireless communication. Themethod may be performed by a base station (e.g., an eNB). At step 1602,the base station generates first control information in a first searchspace. At step 1604, for a first subset of subframes, the base stationassigns a first priority to the first control information in the firstsearch space. The first priority is higher than a second priorityassigned to second control information in a second search space. Thebase station also transmits the first control information with theassigned first priority in the first search space. The first subset ofsubframes may include subframes where a user equipment (UE) may receivereconfiguration information. For example, the first subset of subframesincludes subframes 0, 4, 5, and 9 for a frequency division duplex (FDD)system, and subframes 0, 1, 5, and 6 for a time division duplex (TDD)system.

At step 1606, for a second subset of subframes, the base station assignsa third priority to the first control information in the first searchspace. The third priority is lower than a fourth priority assigned tothe second control information in the second search space. The basestation also transmits the first control information with the assignedthird priority in the first search space. The first search space may bea common search space (CSS) and the second search space may be a userequipment specific search space (UESS). The second subset of subframesmay include subframes where a user equipment (UE) may not receivereconfiguration information.

FIG. 17 is a conceptual data flow diagram 1700 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 1702. The apparatus may be a base station (e.g., an eNB). Theapparatus includes a receiving module 1704, a control informationgenerating module 1706, a coding module 1708, a payload processingmodule 1710, a priority assigning module 1712, and a transmission module1714.

The control information generating module 1706 generates first controlinformation for transmitting in a first search space. The coding module1708 codes the first control information. The coding applied to thefirst control information may be specific to the first search space anddifferent from coding applied to second control information in a secondsearch space. The first search space may be a user equipment specificsearch space (UESS) and the second search space may be a common searchspace (CSS).

The coding module 1708 may apply coding to the first control informationwhen the first control information and the second control informationhave a same set of information fields. Alternatively, the coding module1708 may apply coding to the first control information when the firstcontrol information and the second control information have differentsets of information fields.

Applying the coding to the first control information may include atleast one of: 1) applying rate matching to the first controlinformation, wherein the rate matching applied to the first controlinformation is specific to the first search space and different fromrate matching applied to the second control information in the secondsearch space; 2) interleaving the first control information, wherein theinterleaving applied to the first control information is specific to thefirst search space and different from interleaving applied to the secondcontrol information in the second search space; or 3) scrambling thefirst control information, wherein the scrambling applied to the firstcontrol information is specific to the first search space and differentfrom scrambling applied to the second control information in the secondsearch space. Scrambling the first control information may includescrambling a cyclic redundancy check (CRC) of a first message carryingthe first control information, wherein the scrambling applied to the CRCof the first message is specific to the first search space and differentfrom scrambling applied to the CRC of a second message in the secondsearch space. For example, scrambling may be performed by applying abit-wise exclusive-or (XOR) operation on CRC bits using a scramblingsequence. A scrambling sequence may be specific to the first searchspace and different from a scrambling sequence specific to the secondsearch space. The scrambling sequence may be a pseudo-random sequence.For example, the scrambling sequence may be generated using a Goldsequence generator, where a Gold sequence generator initialization forthe first search space is different from a Gold sequence generatorinitialization for the second search space.

The coding module 1708 may inform (via the transmission module 1714) auser equipment (UE) 1750 of the coding applied to the first controlinformation specific to the first search space. The control informationgenerating module 1706 and/or the coding module 1708 may transmit (viathe transmission module 1714) the coded first control information in thefirst search space.

In an aspect, the payload processing module 1710 may determine a size ofa first payload including the generated control information for thefirst search space. The payload processing module 1710 may also adjustthe size of the first payload to be different from a second payload fora second search space. The first search space may be a user equipmentspecific search space (UESS) and the second search space may be a commonsearch space (CSS). The adjusting the size of the first payload mayinclude adding padding bits to the first payload. The size of the firstpayload may be adjusted when the first payload and the second payloadhave a same set of information fields. Alternatively, the size of thefirst payload may be adjusted when the first payload and the secondpayload have different sets of information fields. The payloadprocessing module 1710 may transmit (via the transmission module 1714)the first payload having the adjusted size in the first search space.

In another aspect, for a first subset of subframes, the priorityassigning module 1712 assigns a first priority to the first controlinformation in the first search space. The first priority may be higherthan a second priority assigned to second control information in asecond search space. The control information generating module 1706transmits (via the transmission module 1714) the first controlinformation with the assigned first priority in the first search space.The first subset of subframes may include subframes where the UE 1750may receive reconfiguration information. For example, the first subsetof subframes includes subframes 0, 4, 5, and 9 for a frequency divisionduplex (FDD) system, and subframes 0, 1, 5, and 6 for a time divisionduplex (TDD) system.

For a second subset of subframes, the priority assigning module 1712assigns a third priority to the first control information in the firstsearch space. The third priority may be lower than a fourth priorityassigned to the second control information in the second search space.The control information generating module 1706 also transmits (via thetransmission module 1714) the first control information with theassigned third priority in the first search space. The first searchspace may be a common search space (CSS) and the second search space maybe a user equipment specific search space (UESS). The second subset ofsubframes may include subframes where the UE 1750 may not receivereconfiguration information.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow charts of FIGS. 14-16.As such, each step in the aforementioned flow charts of FIGS. 14-16 maybe performed by a module and the apparatus may include one or more ofthose modules. The modules may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 18 is a diagram 1800 illustrating an example of a hardwareimplementation for an apparatus 1702′ employing a processing system1814. The processing system 1814 may be implemented with a busarchitecture, represented generally by the bus 1824. The bus 1824 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1814 and the overalldesign constraints. The bus 1824 links together various circuitsincluding one or more processors and/or hardware modules, represented bythe processor 1804, the modules 1704, 1706, 1708, 1710, 1712, 1714, andthe computer-readable medium 1806. The bus 1824 may also link variousother circuits such as timing sources, peripherals, voltage regulators,and power management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1814 may be coupled to a transceiver 1810. Thetransceiver 1810 is coupled to one or more antennas 1820. Thetransceiver 1810 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1810 receives asignal from the one or more antennas 1820, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1814, specifically the receiving module 1704. Inaddition, the transceiver 1810 receives information from the processingsystem 1814, specifically the transmission module 1714, and based on thereceived information, generates a signal to be applied to the one ormore antennas 1820. The processing system 1814 includes a processor 1804coupled to a computer-readable medium 1806. The processor 1804 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium 1806. The software, when executedby the processor 1804, causes the processing system 1814 to perform thevarious functions described supra for any particular apparatus. Thecomputer-readable medium 1806 may also be used for storing data that ismanipulated by the processor 1804 when executing software. Theprocessing system further includes at least one of the modules 1704,1706, 1708, 1710, 1712, and 1714. The modules may be software modulesrunning in the processor 1804, resident/stored in the computer readablemedium 1806, one or more hardware modules coupled to the processor 1804,or some combination thereof. The processing system 1814 may be acomponent of the eNB 610 and may include the memory 676 and/or at leastone of the TX processor 616, the RX processor 670, and thecontroller/processor 675.

In one configuration, the apparatus 1702/1702′ for wirelesscommunication includes means for generating first control informationfor transmitting in a first search space, means for coding the firstcontrol information, wherein the coding applied to the first controlinformation is specific to the first search space and different fromcoding applied to second control information in a second search space,means for transmitting the coded first control information in the firstsearch space, means for informing a user equipment (UE) of the codingapplied to the first control information specific to the first searchspace, means for generating control information for transmitting in afirst search space, means for determining a size of a first payloadincluding the generated control information to be transmitted in thefirst search space, means for adjusting the size of the first payload tobe different from a second payload transmitted in a second search space,means for transmitting the first payload having the adjusted size in thefirst search space, means for informing a user equipment (UE) of theadjusted size of the first payload to be transmitted in the first searchspace, means for generating first control information for transmittingin a first search space, for a first subset of subframes, means forassigning a first priority to the first control information to betransmitted in the first search space, the first priority higher than asecond priority assigned to second control information transmitted in asecond search space, and means for transmitting the first controlinformation with the assigned first priority in the first search space,for a second subset of subframes, means for assigning a third priorityto the first control information to be transmitted in the first searchspace, the third priority lower than a fourth priority assigned to thesecond control information transmitted in the second search space, andmeans for transmitting the first control information with the assignedthird priority in the first search space.

The aforementioned means may be one or more of the aforementionedmodules of the apparatus 1702 and/or the processing system 1814 of theapparatus 1702′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1814 mayinclude the TX Processor 616, the RX Processor 670, and thecontroller/processor 675. As such, in one configuration, theaforementioned means may be the TX Processor 616, the RX Processor 670,and the controller/processor 675 configured to perform the functionsrecited by the aforementioned means.

FIG. 19 is a flow chart 1900 of a method of wireless communication. Themethod may be performed by an apparatus. At step 1902, the apparatusdetermines a first decoding candidate (e.g., first PDCCH candidate) in afirst search space and a second decoding candidate (e.g., second PDCCHcandidate) in a second search space. The first decoding candidate andthe second decoding candidate may have a same size but differentdefinitions of information fields. The first search space may be acommon search space (CSS) and the second search space may be a userequipment specific search space (UESS). Moreover, the first decodingcandidate and the second decoding candidate may have a same startingcontrol channel element (CCE).

At step 1904, the apparatus identifies a difference in the informationfields. At step 1906, the apparatus determines one of the first decodingcandidate and the second decoding candidate as a valid candidate basedon the identified difference.

In an aspect, the difference in the information fields may be realizedat the beginning of a downlink control information (DCI) message.Accordingly, the apparatus may determine that the first decodingcandidate is the valid candidate when the difference occurs at thebeginning of the DCI message. A distinct information field in the DCImessage may be a cross-carrier indicator field (CIF).

In another aspect, the difference in the information fields may berealized towards the end of the DCI message. Accordingly, the apparatusmay determine that the second decoding candidate is the valid candidatewhen the difference occurs towards the end of the DCI message. Adistinct information field in the DCI message may include at least oneof a channel state information (CSI) request field or a soundingreference signal (SRS) request field.

FIG. 20 is a conceptual data flow diagram 2000 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 2002. The apparatus includes a receiving module 2004, acandidate processing module 1206, a difference identifying module 2008,a validity module 2010, and a transmission module 1212.

The candidate processing module 2006 may receive information from a basestation 2050 via the receiving module 2004. The candidate processingmodule 2006 determines a first decoding candidate (e.g., first PDCCHcandidate) in a first search space and a second decoding candidate(e.g., second PDCCH candidate) in a second search space. The firstdecoding candidate and the second decoding candidate may have a samesize but different definitions of information fields. The first searchspace may be a common search space (CSS) and the second search space maybe a user equipment specific search space (UESS). Moreover, the firstdecoding candidate and the second decoding candidate may have a samestarting control channel element (CCE).

The difference identifying module 2008 identifies a difference in theinformation fields. The validity module 2010 determines one of the firstdecoding candidate and the second decoding candidate as a validcandidate based on the identified difference.

In an aspect, the difference identifying module 2008 realizes adifference in the information fields at the beginning of a downlinkcontrol information (DCI) message. Accordingly, the validity module 2010may determine that the first decoding candidate is the valid candidatewhen the difference occurs at the beginning of the DCI message. Adistinct information field in the DCI message may be a cross-carrierindicator field (CIF).

In another aspect, the difference identifying module 2008 realizes thedifference in the information fields towards the end of the DCI message.Accordingly, the validity module 2010 may determine that the seconddecoding candidate is the valid candidate when the difference occurstowards the end of the DCI message. A distinct information field in theDCI message may include at least one of a channel state information(CSI) request field or a sounding reference signal (SRS) request field.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow chart of FIG. 19. Assuch, each step in the aforementioned flow chart of FIG. 19 may beperformed by a module and the apparatus may include one or more of thosemodules. The modules may be one or more hardware components specificallyconfigured to carry out the stated processes/algorithm, implemented by aprocessor configured to perform the stated processes/algorithm, storedwithin a computer-readable medium for implementation by a processor, orsome combination thereof.

FIG. 21 is a diagram 2100 illustrating an example of a hardwareimplementation for an apparatus 2002′ employing a processing system2114. The processing system 2114 may be implemented with a busarchitecture, represented generally by the bus 2124. The bus 2124 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2114 and the overalldesign constraints. The bus 2124 links together various circuitsincluding one or more processors and/or hardware modules, represented bythe processor 2104, the modules 2004, 2006, 2008, 2010, 2012, and thecomputer-readable medium 2106. The bus 2124 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 2114 may be coupled to a transceiver 2110. Thetransceiver 2110 is coupled to one or more antennas 2120. Thetransceiver 2110 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2110 receives asignal from the one or more antennas 2120, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2114, specifically the receiving module 2004. Inaddition, the transceiver 2110 receives information from the processingsystem 2114, specifically the transmission module 2012, and based on thereceived information, generates a signal to be applied to the one ormore antennas 2120. The processing system 2114 includes a processor 2104coupled to a computer-readable medium 2106. The processor 2104 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium 2106. The software, when executedby the processor 2104, causes the processing system 2114 to perform thevarious functions described supra for any particular apparatus. Thecomputer-readable medium 2106 may also be used for storing data that ismanipulated by the processor 2104 when executing software. Theprocessing system further includes at least one of the modules 2004,2006, 2008, 2010, and 2012. The modules may be software modules runningin the processor 2104, resident/stored in the computer readable medium2106, one or more hardware modules coupled to the processor 2104, orsome combination thereof. The processing system 2114 may be a componentof the eNB 610 and may include the memory 676 and/or at least one of theTX processor 616, the RX processor 670, and the controller/processor675. The processing system 2114 may also be a component of the UE 650and may include the memory 660 and/or at least one of the TX processor668, the RX processor 656, and the controller/processor 659.

In one configuration, the apparatus 2002/2002′ for wirelesscommunication includes means for determining a first decoding candidatein a first search space and a second decoding candidate in a secondsearch space, where the first decoding candidate and the second decodingcandidate have a same size but different definitions of informationfields, means for identifying a difference in the information fields,means for determining one of the first decoding candidate and the seconddecoding candidate as a valid candidate based on the identifieddifference, means for determining the first decoding candidate as thevalid candidate, and means for determining the second decoding candidateas the valid candidate.

The aforementioned means may be one or more of the aforementionedmodules of the apparatus 2002 and/or the processing system 2114 of theapparatus 2002′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 2114 mayinclude the TX Processor 616, the RX Processor 670, and thecontroller/processor 675. As such, in one configuration, theaforementioned means may be the TX Processor 616, the RX Processor 670,and the controller/processor 675 configured to perform the functionsrecited by the aforementioned means. The processing system 2114 may alsoinclude the TX Processor 668, the RX Processor 656, and thecontroller/processor 659. As such, in one configuration, theaforementioned means may be the TX Processor 668, the RX Processor 656,and the controller/processor 659 configured to perform the functionsrecited by the aforementioned means.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Further, somesteps may be combined or omitted. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B,C, or any combination thereof” include any combination of A, B, and/orC, and may include multiples of A, multiples of B, or multiples of C.Specifically, combinations such as “at least one of A, B, or C,” “atleast one of A, B, and C,” and “A, B, C, or any combination thereof” maybe A only, B only, C only, A and B, A and C, B and C, or A and B and C,where any such combinations may contain one or more member or members ofA, B, or C. All structural and functional equivalents to the elements ofthe various aspects described throughout this disclosure that are knownor later come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed as a means plus function unless the element is expresslyrecited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication, comprising:determining a first starting index for transmitting first controlinformation in a first search space; determining a second startingindex, different from the first starting index, for transmitting secondcontrol information in a second search space, wherein the secondstarting index is calculated using at least one of a radio networktemporary identifier (RNTI) or a slot; and transmitting the secondcontrol information in the second search space at the second startingindex when the first starting index and the second starting index arenot the same value.
 2. The method of claim 1, wherein the first startingindex is determined based on at least a candidate index and anaggregation level corresponding to the first search space used fortransmitting the first control information.
 3. The method of claim 1,wherein the second starting index is determined based on at least acandidate index and an aggregation level corresponding to the secondsearch space for transmitting the second control information.
 4. Themethod of claim 3, further comprising selecting at least one candidateindex for determining the second starting index that results in a valueof the second starting index that is not the same as a value of thefirst starting index.
 5. The method of claim 1, further comprising:refraining from transmitting the second control information in thesecond search space at the second starting index when the first startingindex and the second starting index are the same value; determining athird starting index for transmitting the second control information inthe second search space by avoiding to use a starting index that has thesame value as the first starting index; and transmitting the secondcontrol information in the second search space at the third startingindex when the first starting index and the third starting index are notthe same value.
 6. The method of claim 1, wherein the second startingindex is for a downlink control information (DCI) format 0 message. 7.The method of claim 1, wherein the first search space is a common searchspace and the second search space is a user equipment (UE) specificsearch space.
 8. An apparatus for wireless communication, comprising:means for determining a first starting index for transmitting firstcontrol information in a first search space; means for determining asecond starting index, different from the first starting index, fortransmitting second control information in a second search space,wherein the second starting index is calculated using at least one of aradio network temporary identifier (RNTI) or a slot; and means fortransmitting the second control information in the second search spaceat the second starting index when the first starting index and thesecond starting index are not the same value.
 9. The apparatus of claim8, further comprising: means for refraining from transmitting the secondcontrol information in the second search space at the second startingindex when the first starting index and the second starting index arethe same value; means for determining a third starting index fortransmitting the second control information in the second search spaceby avoiding to use a starting index that has the same value as the firststarting index; and means for transmitting the second controlinformation in the second search space at the third starting index whenthe first starting index and the third starting index are not the samevalue.
 10. The apparatus of claim 8, wherein the first starting index isdetermined based on at least a candidate index and an aggregation levelcorresponding to the first search space used for transmitting the firstcontrol information.
 11. The apparatus of claim 8, wherein the secondstarting index is determined based on at least a candidate index and anaggregation level corresponding to the second search space fortransmitting the second control information.
 12. The apparatus of claim11, further comprising selecting at least one candidate index fordetermining the second starting index that results in a value of thesecond starting index that is not the same as a value of the firststarting index.
 13. An apparatus for wireless communication, comprising:a memory; and at least one processor coupled to the memory andconfigured to: determine a first starting index for transmitting firstcontrol information in a first search space; determine a second startingindex, different from the first starting index, for transmitting secondcontrol information in a second search space, wherein the secondstarting index is calculated using at least one of a radio networktemporary identifier (RNTI) or a slot; and transmit the second controlinformation in the second search space at the second starting index whenthe first starting index and the second starting index are not the samevalue.
 14. The apparatus of claim 13, the at least one processor furtherconfigured to: refrain from transmitting the second control informationin the second search space at the second starting index when the firststarting index and the second starting index are the same value;determine a third starting index for transmitting the second controlinformation in the second search space by avoiding to use a startingindex that has the same value as the first starting index; and transmitthe second control information in the second search space at the thirdstarting index when the first starting index and the third startingindex are not the same value.
 15. The apparatus of claim 13, wherein thefirst starting index is determined based on at least a candidate indexand an aggregation level corresponding to the first search space usedfor transmitting the first control information.
 16. The apparatus ofclaim 13, wherein the second starting index is determined based on atleast a candidate index and an aggregation level corresponding to thesecond search space for transmitting the second control information. 17.The apparatus of claim 16, further comprising selecting at least onecandidate index for determining the second starting index that resultsin a value of the second starting index that is not the same as a valueof the first starting index.
 18. A non-transitory, computer-readablemedium storing computer-executable code, comprising code to: determine afirst starting index for transmitting first control information in afirst search space; determine a second starting index, different fromthe first starting index, for transmitting second control information ina second search space, wherein the second starting index is calculatedusing at least one of a radio network temporary identifier (RNTI) or aslot; and transmit the second control information in the second searchspace at the second starting index when the first starting index and thesecond starting index are not the same value.
 19. The computer-readablemedium of claim 18, further comprising code to: refrain fromtransmitting the second control information in the second search spaceat the second starting index when the first starting index and thesecond starting index are the same value; determine a third startingindex for transmitting the second control information in the secondsearch space by avoiding to use a starting index that has the same valueas the first starting index; and transmit the second control informationin the second search space at the third starting index when the firststarting index and the third starting index are not the same value. 20.The computer-readable medium of claim 18, wherein the first startingindex is determined based on at least a candidate index and anaggregation level corresponding to the first search space used fortransmitting the first control information.
 21. The computer-readablemedium of claim 18, wherein the second starting index is determinedbased on at least a candidate index and an aggregation levelcorresponding to the second search space for transmitting the secondcontrol information.
 22. The computer-readable medium of claim 21,further comprising selecting at least one candidate index fordetermining the second starting index that results in a value of thesecond starting index that is not the same as a value of the firststarting index.